1. Field of the Invention
The invention relates to a measuring apparatus.
2. Description of the Related Art
In general, imaging apparatus using X-rays, ultrasonic waves, or nuclear magnetic resonance imaging technique (MRI) are used commonly in the medical field. On the other hand, study has been pursued actively on an optical imaging apparatus that acquires in-vivo information by propagating, through a living subject, light, such as laser light, from a light source and with which a living body has been irradiated, and detecting the propagated light. An example of an optical imaging technique includes photoacoustic tomography (PAT).
In PAT, a subject is irradiated with pulsed light that is generated from a light source to detect temporal variations in acoustic waves (typically, ultrasonic waves) generated from living tissue which has absorbed the energy of the light propagated and diffused inside the subject at a plurality of portions surrounding the subject. Then, the information regarding the optical characteristic values of the subject is visualized through a process of mathematically analyzing the detected signals. Thus, since it is possible to obtain an initial pressure generation distribution or a light energy absorption density distribution generated when the subject is irradiated with light, the position of a malignant tumor caused due to new vascular reproduction can be designated. The term “photoacoustic imaging apparatus” herein refers to an imaging apparatus that uses the PAT technique.
In general, in PAT, there is a closed surface (particularly, many points on a spherical measurement surface) surrounding or enclosing the entire subject. Therefore, it is desirable to measure a temporal variation in acoustic waves using an ideal acoustic wave detecting unit (broad-band and point detection). By performing processing using an image reconstruction method based on the measured result, an initial acoustic pressure distribution generated by light irradiation can completely be visualized in theory.
U.S. Pat. No. 6,607,489 discloses correction in image reconstruction.